JP2007268831A - Mold and method of manufacturing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost and high-precision mold capable of forming a plurality of patterns at once, and a method of manufacturing the mold. <P>SOLUTION: A first layer film 120 is formed on the surface of a substrate 110 and a second layer film 130 is formed on the surface of the first layer film 120, by direct bonding by interface activation. The substrate 110, the first layer film 120 and the second layer film 130 are formed of materials of the same substance and have different plane directions. Then, a resist layer 140 is formed on the surface of the second layer film 130 and the surface of the resist layer 140 is irradiated with an electron beam A for exposure. Then, a dry etching or a wet etching is applied to the second layer film 130 by using a pattern 150 formed on the resist layer 140 as a mask. Next, the resist layer 140 is peeled to form a pattern constituted of unevenness on the surface of the second layer film 130. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mold used for nanoimprinting and production thereof.

  In the field of manufacturing semiconductors and the like, it is desired to efficiently form a fine resist pattern for use in photolithography. However, in the conventional photolithography, it is necessary to go through a process with a large number of steps and types of materials used.

In view of this, nanoimprint lithography (hereinafter referred to as NIL) in which a resist pattern is formed by an imprint mold, that is, a mold, has been proposed.
The NIL mold is manufactured by etching a substrate such as silicon or quartz to form a concavo-convex pattern on the surface of the substrate. The concavo-convex pattern has been miniaturized and complicated, and a plurality of concavo-convex patterns have been required to be transferred.

  When forming a concavo-convex pattern on a single substrate of the same material, multiple concavo-convex patterns are transferred and etched repeatedly, but in this process, the depth and height of the concavo-convex pattern are constant. Often difficult.

  FIG. 7 shows a conventional mold manufacturing method. When the mold 100 as shown in FIG. 1 is manufactured, the conventional manufacturing method is as follows. First, a resist layer 20 is formed on the substrate 10 as shown in FIG. The substrate 10 is made of a material such as silicon or quartz, for example. Next, as shown in FIG. 7B, the resist layer 20 is exposed, developed, etc., and a pattern 30 is formed on the resist layer 20. Next, as shown in FIG. 7C, etching is performed on the substrate 10 using the resist layer 20 on which the pattern is formed as a mask. That is, the recesses 50 and 55 are formed on the substrate 10 by etching the recesses 40 and 45 formed in the resist layer 20. Next, as shown in FIG. 7D, the resist layer 20 is peeled off.

  Next, as shown in FIG. 7E, a resist layer 60 is formed on the substrate 10 on which the uneven pattern is formed. Next, as shown in FIG. 7F, the resist layer 60 is exposed and developed to form a pattern 70 on the resist layer 60. Next, as shown in FIG. 7G, etching is performed on the substrate 10 using the patterned resist layer 60 as a mask. That is, the surface 90 is formed by etching the portion of the surface 80 on the resist layer 60.

  Next, as shown in FIG. 7H, the resist layer 60 is peeled off, and a plurality of uneven patterns are formed on the substrate 10 to form a mold. In order to perform highly accurate nanoimprinting, it is desirable that the depth of the unevenness in the pattern formed in one etching process is constant. That is, it is desirable that the surface 55 and the surface 95 have a constant height. However, the heights of the uneven surface 55 and the surface 95 are not constant.

8 is an enlarged view of a part of FIG. 7 (c), and FIG. 9 is an enlarged view of a part of FIG. 7 (g). As shown in FIG. 8, the pattern 30 formed on the resist layer 60 has recesses having two areas of S ₁ and S ₂ . When patterns having different areas are present on the same plane, the etching rate is faster in the portion having a larger area.
Therefore, the depth d ₁ of the surface 95 is larger than the depth d _{2 of the} surface 55 as shown in FIG. When the depths are different in this way, it is difficult to perform accurate nanoimprinting.

Also, the production of a plurality of molds requires cost. In addition, in order to transfer a pattern using a plurality of molds, transfer is required for the number of molds, so that the efficiency is poor. Therefore, in order to efficiently form a plurality of concavo-convex patterns at a low cost, etching is performed several times by using a layered body in which a plurality of substances having different selection ratios, that is, etching rates are stacked, and using the difference in selection ratios. A method of repeating has been proposed (see, for example, “Patent Document 1”).
JP 2004-71587 A

  However, in the case of using a laminate in which different substances are laminated as described above, when energy is applied to the mold due to friction or heat during transfer, a stress is applied in the horizontal direction with respect to the interface of each layer due to the difference in thermal expansion coefficient. work. As a result, there is a problem that distortion occurs in the concavo-convex pattern.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a low-cost and high-precision mold and a mold manufacturing method capable of forming a plurality of patterns at a time. It is in.

  In order to achieve the above-mentioned object, a first invention is a mold used for nanoimprinting, which is a laminate in which two or more types of layers are stacked on a substrate, and the two or more types of layers have different surfaces. It is a mold characterized in that it is made of the same material having an orientation.

  The boundary between the adjacent layers forms an uneven bottom or top surface. Since the etching stops at the boundary of the layers, a recess from the top surface to the bottom of one layer is formed in one etching. That is, the unevenness forming one pattern does not extend over a plurality of layers.

    The plane orientation of the layer is preferably a combination of Miller indices {100}, {111}, {110}, {331}.

  The material of the mold is a single crystal semiconductor material or diamond.

  Adjacent layers are joined together by direct joining by interfacial activation.

  Further, the adjacent layers may be bonded by metal bonding in which a metal thin film is disposed between materials to be bonded and bonded by heating and pressing. Further, when the material to be bonded is silicon, siloxane bonding using a silicon oxide film as the bonding material may be used. However, metal bonding and siloxane bonding are limited to conditions under which stress due to a difference in thermal expansion coefficient and lattice mismatch with respect to the bonding interface can be ignored.

  The layers are laminated such that the etching rate of the layer in contact with the substrate is the slowest, and the etching rate becomes slower as the layer is separated from the substrate.

  A second invention is a method for producing a mold used for nanoimprinting, wherein a laminate is produced by laminating layers made of the same material having two or more different plane orientations on a substrate, and the laminate Forming a resist layer on the surface of the substrate, forming a resist pattern on the resist layer, etching the laminate using the resist pattern as a mask, and forming a pattern composed of irregularities on the laminate And forming the mold.

  According to the present invention, it is possible to provide a low-cost and high-precision mold and a mold manufacturing method capable of forming a plurality of patterns at a time.

  Hereinafter, a mold 100 and a method for producing the mold 100 according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of a mold 100. The mold 100 is used for nanoimprinting.

2 and 3 are diagrams showing each step of the method for manufacturing the mold 100 according to the present invention.
First, as shown in FIG. 2A, a substrate 110 is prepared. The substrate 110 is a crystalline material and is made of a material such as silicon or diamond.

Next, as shown in FIGS. 2B and 2C, the first layer film 120 is formed on the surface of the substrate 110, and the second layer film 130 is formed on the surface of the first layer film 120. The first layer film 120 and the second layer film 130 have the same material as the substrate 110 and crystals having different plane orientations. The combinations of plane orientations exist as much as possible, but in practice, any layer having a different selectivity (etching rate) may be used. It is preferable to combine four layers having plane orientations indicated by the Miller indices {100}, {111}, {110}, and {331} (the Miller indices will be described later with reference to FIG. 4). In particular, it is preferable to combine any of {111} and {331} with respect to {100} and {110}.
Two types of plane orientation materials may be alternately repeated, or three or more types of plane orientation materials may be used. In addition, it is not necessary to consider the plane orientation of the substrate 110 on which the unevenness is not produced.

  When materials having the same material and different plane orientations are stacked, the selection ratio (etching speed) differs depending on the material, so that the etching can be accurately stopped at the boundary between the layers.

  The substrate 110 and the first layer film 120, and the first layer film 120 and the second layer film 130 are bonded together. Each layer is prepared separately in advance, and then each layer is bonded. As a bonding method, direct bonding by interface activation is most preferable. Examples of the surface activation include a plasma processing method and a processing method using an ion beam.

  For bonding, a method other than direct bonding by interface activation can be used under the condition that stress caused by a difference in thermal expansion coefficient and lattice mismatch with respect to the bonding interface can be ignored.

  The following two methods can be considered as methods other than direct bonding by surface activation. One is metal bonding in which a metal thin film is arranged between materials to be bonded and bonded by heating and pressurizing. The other is siloxane bonding using a silicon oxide film as the bonding material when the material to be bonded is silicon. Since these include a material different from the material to be bonded at the bonding interface, the stress applied to the interface is not strictly zero. However, it is known that the stress is reduced if the material used for bonding is sufficiently thin.

  Therefore, if the film thickness is sufficiently thin compared to the depth of the unevenness to be produced and the stress on the material is negligible with respect to the pattern displacement, metal bonding, siloxane bonding, etc. are performed. Also good.

  Next, as shown in FIG. 2D, a resist layer 140 is formed on the surface of the second layer film 130. The resist layer 140 is formed by a method such as spin coating or spray coating. Next, the surface of the resist layer 140 is irradiated with an electron beam A and exposed. Examples of the exposure method include exposure using an electron beam, exposure using a laser drawing machine, exposure using ultraviolet light using a mask, and the like. Next, as shown in FIG. 2E, a process such as development is performed to form a pattern 150 on the resist layer 140. As a result of development, a recess 160, that is, an exposed portion of the second layer film 130 is formed on the resist layer 140.

  Next, as shown in FIG. 2F, the second layer film 130 is etched using the pattern 150 formed in the resist layer 140 as a mask. That is, the recesses 170-1, 170-2, and 170-3 are formed on the second layer film 130 by etching the recesses 160-1, 160-2, and 160-3. If there is a sufficient selection ratio (difference in etching rate) between the second layer film 130 and the first layer film 120, the etching stops at the boundary between the first layer film 120 and the second layer film 130.

In this case, the second layer film 130 and the first layer film 120 are the same material with different plane orientations, and the etching rates are different. In the case of a substrate formed of a conventional single material, etching is performed if the area S _{4 of the} recess 160-2 is different from the areas S ₃ and S ₅ of the recesses 160-1 and 160-3. The depth of the subsequent recess is different. The area of the recess as the rate of etching becomes faster wide, large concave area, for example, recess 160-1 of area _{S 3,} the etching depth of the partial recess 160-3 of the area _{S 5} of area _{S 4} It becomes deeper than the recess 160-2. However, according to the method of the present invention to laminate layers having different etch rates, the recess 160-1 of area S _3, for even recess 160-3 of the area S _5, it is possible to stop the etching at the boundary of the layer may be it is possible to align the etching depth of the recess 160-2 of the area _{S 4,} equal the depth of the recess 170-1,170-2,170-3 after etching.

Etching may be either dry etching or wet etching. In the case of dry etching, as the etching gas, a fluorine-based gas such as CF ₄ , SF ₆ , or CHF ₃ , a chlorine-based gas such as Cl ₂ or CCl ₄ , a bromine-based gas such as HBr, etc. are generally used. In consideration of the selection ratio in the silicon laminate, it is preferable to use a gas obtained by adding oxygen (O ₂ ) to odorous acid (HBr) and tetrachloromethane (CCl ₄ ).
In the case of wet etching, the chemical solution is preferably potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) that can easily obtain a selection ratio. However, in this case, if the substrate is a single crystal, the etching sidewall is formed by a facet surface corresponding to the plane orientation.
Note that in the case of performing wet etching, the resist often has insufficient resistance to the above chemicals. Therefore, a silicon compound such as a silicon nitride film (SiN) or a silicon oxide film (SiO ₂ ) or a metal film such as chromium (Cr), tantalum (Ta), or titanium (Ti) is processed to form the resist layer 140. An alternative is desirable.

Next, the resist layer 140 is removed as shown in FIG. If the mold has a single pattern, the manufacturing process ends here. In the case of forming a plurality of uneven patterns on the mold, the steps from applying the resist are further repeated. As shown in FIG. 3H, a resist layer 180 is formed on the surface of the second layer film 130. Next, the electron beam A is irradiated. As described above, exposure using a laser drawing machine or exposure using ultraviolet light using a mask may be performed.
Next, as illustrated in FIG. 3I, development processing is performed to form a pattern 190 on the resist layer 180.

Next, as shown in FIG. 3J, the first layer film 120 is etched using the pattern 190 on the resist layer 180 as a mask. That is, the recesses 210-1 and 210-2 are formed on the first layer film 120 by etching the recesses 200-1 and 200-2 formed in the resist layer 180.
As described above, the depths of the recesses 210-1 and 210-2 can be made constant regardless of the size of the area.
Next, the resist layer 180 is peeled off as shown in FIG.

  As described above, the mold 100 is manufactured by stacking two or more layers of the same substance having different plane orientations, applying a resist to form a pattern, and performing etching.

Next, the plane orientation will be described with reference to FIG. FIG. 4 is a schematic diagram showing the relationship between the crystal axis and the plane 300.
One method for describing the plane and direction of a crystal is the Miller index, which shows the relationship between the crystal plane and the intersection of crystal axes X, Y, and Z.

  For example, when the surface 300 shown in FIG. 4 is described by the Miller index, the surface 300 intersects the X axis and the Y axis at 2 and the Z axis intersects at 3. Therefore, the Miller index takes the reciprocal number of each. (1/2 1/2 1/3).

  However, since the Miller index is expressed by a relatively prime integer, it is converted into an integer and described as (332).

  In this embodiment, in order to obtain different selection ratios, layers having plane orientations indicated by Miller indices {100}, {111}, {110}, and {331} are used.

  Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a diagram showing formation of a recess when the mold 100 is manufactured, and FIG. 6 is a diagram showing formation of a recess when a mold is manufactured with a single material according to a conventional manufacturing method.

  In FIG. 5, a single crystal silicon wafer was used as the substrate 110a. The plane orientation of the silicon surface of the substrate 110a was {111}. A first layer film 120a was formed on the surface of the substrate 110a. The plane orientation of the silicon surface of the first layer film 120a was {100}. The substrate 110a and the first layer film 120a were directly joined. Direct bonding was performed by performing surface treatment with plasma using a mixed gas of hydrogen and helium and then heating at 300 ° C. in a vacuum. After directly bonding the substrate 110a and the first layer film 120a, the first layer film 120a was polished to 200 nm.

A resist was applied to the laminate of the substrate 110a and the first layer film 120a, and a pattern was formed by an electron beam. The pattern was a square hole, and two patterns with a width of 300 nm and 75 nm were formed.
Next, the pattern was processed by dry etching. As an etching gas, a mixed gas of HBr and O ₂ was used. At this time, the time was set so that the etching depth of the pattern having a width of 75 nm was 200 nm.

  As a result of observing the cross section with a scanning electron microscope (SEM), as shown in FIG. 5B, etching of both the recesses 310 having a width of 75 nm and the recesses 320 having a width of 300 nm was stopped at a depth of 200 nm. .

Similarly, a test was performed by wet etching with TMAH. The surface of the laminate was covered with silicon nitride (SiN) formed by CVD, a resist was applied to the surface, exposed and developed to form a pattern. The pattern was a square hole, and two patterns with a width of 20 μm and 3.0 μm were formed. The exposure method used ultraviolet (UV) transfer using a photomask. The SiN portion was etched with a mixed gas of CF ₄ and H ₂ .

  As a result, as shown in FIG. 5C, the etching was stopped at the depth of 200 nm in both the recess 330 having a width of 3.0 μm and the recess 340 having a width of 20 μm.

  In FIG. 6, a single crystal silicon wafer having a plane orientation (100) was used as the substrate 110b. A resist was applied in exactly the same manner as in FIG. 5 to form a pattern, and both dry etching and wet etching were tested.

  In the case of dry etching, as shown in FIG. 6B, the depth of the recess 350 having a width of 75 nm was 200 nm, whereas the depth of the recess 360 having a width of 300 nm was 241 nm.

  In the case of wet etching, as shown in FIG. 6C, the depth of the recess 370 having a width of 3.0 μm was 203 nm, whereas the depth of the recess 380 having a width of 20 μm was 262 nm.

  From these results, when etching was performed on a substrate made of one kind of material, the etching depth changed depending on the size of the aperture of the recess, but the layered body was made by laminating layers of the same substance with different plane orientations. When etching was performed, the etching depth could be made constant regardless of the size of the diameter of the recess.

  As described above, by stacking the same materials having different plane orientations, the etching depth can be accurately adjusted. That is, even if the materials are the same, if the materials having different crystal plane orientations are stacked, the selection ratio (etching speed) differs depending on the materials, so that the etching stops at the boundary between the layers. For this purpose, however, the substrate side, that is, the lower layer side, needs to have a lower etching rate than the upper layer side. Moreover, when forming a some uneven | corrugated pattern, it becomes possible to arrange | equalize the depth of each pattern uniformly by laminating | stacking three or more layers. Therefore, it is possible to accurately form a plurality of concave and convex patterns with one mold, and it is not necessary to repeat imprinting with a plurality of molds.

  Moreover, the thermal expansion coefficient can be made constant by stacking the same substances. Thereby, it is possible to prevent the concavo-convex pattern from being distorted due to the difference in thermal expansion coefficient.

  The preferred embodiments of the mold and the method for producing the mold according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

Schematic diagram of mold 100 according to the present embodiment The figure which shows the process of preparation of the mold 100 which concerns on this Embodiment. The figure which shows the process of preparation of the mold 100 which concerns on this Embodiment. Diagram showing the coordinate axis of the plane orientation The figure which shows the recessed part of the mold in an Example The figure which shows the recessed part of the mold produced in the Example by the conventional method Diagram showing conventional mold manufacturing method The figure which expanded the process of FIG.7 (c) The figure which expanded the process of FIG.7 (g)

Explanation of symbols

100 ......... Mold 10, 110 ......... Substrate 20, 140 ......... Resist layer 30, 70, 150, 190 ......... Pattern

Claims (16)

A mold used for nanoimprinting,
It consists of a laminate in which two or more layers are laminated on a substrate,
The mold is characterized in that the two or more types of layers are made of the same material having different plane orientations.   The mold according to claim 1, wherein a boundary between adjacent layers forms an uneven bottom or top surface.   The mold according to claim 1, wherein the plane orientation of the layer is a combination of {100}, {111}, {110}, and {331}.   The mold according to claim 1, wherein the mold is made of a semiconductor material or diamond.   2. The mold according to claim 1, wherein the adjacent layers are bonded to each other by direct bonding by interface activation.   The mold according to claim 1, wherein the adjacent layers are bonded to each other by metal bonding.   The mold according to claim 1, wherein the adjacent layers are bonded to each other by siloxane bonding.   The layer is stacked such that when the layers are stacked, the etching rate of the layer in contact with the substrate is the slowest, and the etching rate decreases as the layer is separated from the substrate. mold. A method for producing a mold used for nanoimprinting,
Stacking layers of the same material having two or more different plane orientations on a substrate to produce a laminate;
Forming a resist layer on the surface of the laminate;
Forming a resist pattern on the resist layer;
Etching the stack using the resist pattern as a mask, and forming a pattern composed of irregularities on the stack; and
A method for producing a mold comprising:   The method for producing a mold according to claim 9, wherein the step of etching the substrate is performed such that a boundary between adjacent layers forms an uneven bottom or top surface.   The method for producing a mold according to claim 9, wherein the plane orientation of the layer is a combination of {100}, {111}, {110}, and {331}.   The method for producing a mold according to claim 9, wherein the mold is made of a semiconductor material or diamond.   The method for producing a mold according to claim 9, wherein the adjacent layers are bonded to each other by direct bonding by interfacial activation.   The method for producing a mold according to claim 9, wherein the adjacent layers are bonded to each other by metal bonding.   The method for producing a mold according to claim 9, wherein the adjacent layers are bonded to each other by siloxane bonding.   10. The layer according to claim 9, wherein the layers are stacked such that the etching rate of the layer in contact with the substrate is the slowest and the etching rate decreases as the layer is separated from the substrate. Mold production method.

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